So I’m new to this, have a pioneer ddj-sb and a midi fighter twister. I alternate between using my Desktop and my laptop. I keep all my music stored in an USB flash drive so i can move it from one computer to another and so my current problem is, this is fine with my laptop as it has 4 usb ports but my desktop has only 2 in the front. Would it be fine to use a USB expander? I would not run both controllers through the expander, it would be Midi (5v 250mA) + flashdrive on expander and ddj-sb (5v 500mA) on the other port.
Do you mean USB hub? You should be fine. If you run into problems, you can get powered USB hub (one that has its own power supply), so all your devices can get maximum power from the USB.
This, just get a powered usb hub, Ive just recently bought a Belkin 7port one and it works fine with an S4, X1, F1, MF3D, and external harddrive attached
use a powered hub for all MIDI/HID controllers without an audio interface but you should always connect your sound card (in this case your S4) directly to a USB port on your computer to minimize audio latency.